The unique giant Irish moss (Chondrus crispus) from Basin Head: health assessment in relation to reference sites on Prince Edward Island

Abstract

Irish moss (Chondrus crispus Stackhouse) is a red alga that is common in Atlantic Canada. A unique strain of this species, the giant Irish moss, grows in a single location and is under strict protection. Unlike the common coastal form, the giant Irish moss reproduces solely by fragmentation and is found in gametophyte form. A 99.9% decline in giant Irish moss abundance (1999–2012) prompted this study to address two questions: whether the giant Irish moss remains 100% vegetative and gametophytic, and whether such decline is related to factors leading to a reduction in photosynthetic health. Six populations of the common Irish moss strain were compared with two populations of giant Irish moss, and their life history phases determined using a resorcinol method. The common Irish moss populations exhibited a 65%–86% ratio of gametophytic:tetrasporophytic fronds, while both giant strain populations were 100% gametophytic. Photosynthetic efficiency was measured with Pulse-Amplitude-Modulation (PAM) fluorometry and neither giant moss population had significantly different quantum yield values from the littoral populations. Hence, these analyses provided no evidence of giant Irish moss being exposed to particular sources of stress linked to water or habitat quality and alternative factors explaining the decline of this unique strain are proposed.